These are different types of services that phones offer, such as the ability to put calls on hold, call waiting, and caller-ID.
Supplementary Service
Call Transfer (H.450.2), Call Hold (H.450.4), Call Pick-up (H.450.5), Call Waiting (H.450.6), Name Identification (H.450.8), Call Intrusion (H.450.11)
Buttons
Redial, Mute, Hold, Transfer, Conference
Some IP phones come with extra features such as a phonebook, SMS messaging, or a built in answering machine.
Additional Features
Hand Free Mode, Speaker, Voice Mail
